Managing HP Serviceguard for Linux, Seventh Edition, July 2007

Understanding Serviceguard Software Components
Serviceguard Architecture
Chapter 3 37
Cluster Object Manager Daemon: cmomd
This daemon is responsible for providing information about the cluster to
clients—external products or tools that depend on knowledge of the state
of cluster objects. Clients send queries to cmomd and receive responses
from it.
Clients send queries to the object manager and receive responses from it
(this communication is done indirectly, through a Serviceguard API). The
queries are decomposed into categories (of classes) which are serviced by
various providers. The providers gather data from various sources,
including, commonly, the cmclconfd daemons on all connected nodes,
returning data to a central assimilation point where it is filtered to meet
the needs of a particular query.
This daemon is started by xinetd. Parameters are in the
/etc/xinetd.d/hacl-probe file. The path for this daemon is
$SGLBIN/cmomd.
This daemon may not be running on your system; it is used only by
clients of the object manager.
Service Assistant Daemon: cmsrvassistd
This daemon forks and execs any script or processes as required by the
cluster daemon, cmcld. There are two type of forks that this daemon
carries out:
• Executing package run and halt scripts
• Launching services
For services, cmcld monitors the service process and, depending on the
number of service retries, cmcld either restarts the service through
cmsrvassistd or it causes the package to halt and moves the package to
an available alternate node. The path for this daemon is:
$SGLBIN/cmsrvassistd.
Quorum Server Daemon: qs
The quorum server daemon provides tie-breaking services when needed
during cluster re-formation. The quorum server runs on a system
external to the cluster, and it is started by the user, not by Serviceguard.
It is normally started out of /etc/inittab, which means that it
automatically re-spawns if it fails or is killed. Additionally, the quorum
server can be run in a package in another cluster.